Original Pudong CDC U Health

Do you know how to disinfect tap water?

A lot of chemically good U powder needs to be answered first:

Chlorine!

If you think so,

That’s too underestimate the tap water.

Let’s study with Xiao U today ~

How much do you know about disinfection methods of tap water?

With the improvement of people’s living standards, cities are making efforts to improve the quality of drinking water. A survey on the disinfection of urban tap water shows that at present, most urban tap water is still mainly disinfected by traditional chlorine (including liquid chlorine and bleaching powder disinfection, etc.), and chlorine dioxide is used instead in some areas, or ozone disinfection and ultraviolet disinfection have been used for advanced treatment.

Disinfection

Refers to the method of killing pathogenic microorganisms in the external environment. The purpose of disinfection of drinking water is to consider the pollution of pathogenic bacteria in every link of water supply process, and to cut off the transmission route of pathogenic microorganisms in drinking water through disinfection to prevent the occurrence and prevalence of infectious diseases.

At present, the main disinfection methods for drinking water in China are chlorination disinfection, chlorine dioxide disinfection, ultraviolet disinfection and ozone disinfection.

Which disinfection method is stronger?

1, the traditional chlorination (chlorination)

Chlorination disinfection

It refers to a method of disinfection of drinking water with chlorine or chlorine preparation, which is the most widely used and mature method in drinking water disinfection.

Chlorine preparations mainly include: sodium hypochlorite, bleaching powder, liquid chlorine and organic chlorine preparations. Their sterilization mechanism is basically the same. Mainly depends on the hydrolysis product hypochlorous acid.

Chlorination disinfection, as one of the commonly used disinfection technologies of tap water, has the characteristics of simple use, easy procurement of raw materials and good continuous sterilization effect, so it occupies a large market in waterworks in China. Although people pay more and more attention to the side effects of chlorine disinfection with the strengthening of people’s health awareness, chlorine may still be one of the most common disinfectants used in underdeveloped areas for a long time.

2. Chlorine dioxide (ClO2) disinfection.

People pay more and more attention to the environmental and safety problems caused by chlorine disinfection. Among the available disinfectants, chlorine dioxide is considered to be the most cost-effective one.

Advantages and disadvantages of ClO2 _ 2 disinfection:

Advantages:

Good sterilization effect, small dosage and long action time, and can keep the remaining disinfection dose;

It can reduce the formation of chlorinated by-products such as trihalomethane and haloacetic acid in water. When the water contains ammonia, it does not react with ammonia, and its disinfection effect is not affected;

Strong oxidation, can decompose cell structure and kill spores and viruses, especially for cryptosporidium and Giardia;

After disinfection, the residual chlorine in the water is stable and lasting, and the ability to prevent re-pollution is strong;

Can remove the color and taste in water, and does not form chlorophenol odor with phenol;

The effect of removing iron and manganese is stronger than that of chlorine.

Disadvantages:

ClO2 is explosive and must be prepared on site and used immediately; Chlorate and chlorite can be produced.

The application of chlorine dioxide in drinking water treatment in China has gradually attracted people’s attention, and the promotion of chlorine dioxide as a conventional optional disinfectant in water plants in China is also an inevitable trend.

3, ultraviolet disinfection

Ultraviolet rays with wavelength of 200~280nm have bactericidal effect, among which ultraviolet rays with wavelength of 254nm have the strongest bactericidal effect. Ultraviolet disinfection technology is one of the physical disinfection methods. Its advantages are short contact time and high sterilization efficiency. Does not produce toxic and harmful substances, has broad-spectrum sterilization ability and no secondary pollution; The disinfection effect is not affected by water temperature and pH. The disadvantage is that it has no continuous disinfection effect, needs to be used in conjunction with chlorine, and is expensive.

Ultraviolet disinfection was first applied in the United States, and now it has become a mature, reliable, efficient and environmentally friendly disinfection technology. It has been widely used in various fields abroad, but it has not been popularized in China.

4, Ozone (ozone) disinfection

Ozone is a very strong oxidant.

Advantages and disadvantages of O3 disinfection:

Advantages: the disinfection effect is better than that of ClO2 and Cl2, and the dosage is less; The pH value is between 6 and 8.5. Does not affect the sensory properties of water, but also has many functions such as deodorization, color, iron, manganese, phenol and so on; No trihalomethane is generated; When used in pretreatment, it can also promote flocculation and clarification and reduce the dosage of coagulant.

Disadvantages: large investment and higher cost than chlorination disinfection; O3 in water is unstable and easy to decompose, and it needs certain technology to control and detect O3. The retention time in water is very short, which can not maintain the continuous disinfection effect of the pipe network and requires a second disinfectant.

How to disinfect tap water in Pudong?

At present, there are 8 waterworks in Pudong New Area, which use Qingcaosha Reservoir as the water source in a unified way, and the tap water is disinfected by chloramine.

Chloramine disinfection is a kind of chlorination disinfection.

Advantages: less disinfection by-products, better taste and chroma of water, higher stability, and guaranteed residual chlorine in the pipe network, which is suitable for long-distance water supply plants.

Disadvantages: chloramine is a weak oxidant, and its disinfection effect is not as strong as hypochlorous acid, which requires higher concentration and longer contact time; The operation of adding ammonia is complicated, and the effect of killing virus is poor.

In addition to water treatment process

Besides the conventional coagulation-sedimentation-filtration-disinfection,

And advanced treatment technology of drinking water,

That is, in order to further improve the quality of drinking water,

Treatment of macromolecular organic matter in drinking water.

Commonly used advanced treatment technology of drinking water

Ozone-activated carbon technology,

Membrane separation technology, biological activated carbon technology, etc.

For more details, listen to Xiao u’s next breakdown ~

References:

[1] Water World-www.chinacitywater.org/, China Urban Water Network

[2] Yang Kedi. Environmental Hygiene [M], Beijing, People’s Health Publishing House.

The picture comes from the Internet.

Contributed by: Yang Minjuan, Environmental and Occupational Hazard Factor Control Section

Reviewer: Huang Yunbiao and Shen Huiping

Original title: "How to disinfect tap water in Pudong? Is it safe enough? 》

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